Electrochemical immunoassay on expression of integrin β1 on tumor cells and drug-resistant tumor cells

An electrochemical indirect competitive immunoassay protocol as a promising cytosensing strategy was developed to detect integrin β1 expression on human breast cancer MCF-7 cells and adriamycin-resistant human breast cancer MCF-7 (MCF-7/ADR) cells and quantify the cell number. Integrin α5β1 was adsorbed on the gold-nanoparticle modified glassy carbon electrode to bind integrin β1 monoclonal antibody (anti-CD29 mAb). A sandwich structure was then formed using nanocomposites which consisted of horseradish peroxidase (HRP) labeled anti-antibody and gold nanoparticles. HRP bound on the electrode surface could cause an amperometric response of the hydroquinone–H2O2 system. The assembly of the sandwich structure was inhibited by tumor cells to give decreased enzyme-catalytic signals due to the capture of anti-CD29 mAb by integrin β1 on cell membranes. Under optimal conditions the relative current change (S) was proportional to the cell concentration from 1.6×103 to 2.0×106 cells mL−1 with a detection limit of 700 cells mL−1. Integrin β1 expression in MCF-7/ADR cells was found to be significantly higher than that in MCF-7 cells, indicating the increased adhesion ability of MCF-7/ADR cells.

► An electrochemical immunoassay for integrin β1 on cell membrane was performed.
► The formation of sandwich structure on the electrode surface was inhibited by cells.
► The decline degree of electrochemical signals was used to quantify the cell number.
► Integrin β1 expression in MCF-7/ADR cells is higher than that in MCF-7 cells.